A mobile station communicating with a wireless entity such as a base station or a target mobile station sometimes undergoes a reselection. The reselection is a handover such that the mobile station is communicating with a different base station or in a different sector. The mobile station may also undergo a seamless transition whereby communication from the base station is switched over from a first device of the mobile station to a second device. For example, a user can sometimes switch over from communicating with the base station via a first cellular telephone to a second cellular telephone. Alternatively, the user could switch over from talking via a handheld telephone receiver to talking via a speaker phone.
During the interval before a reselection many current systems continue normal video, background, packet header, audio, presence, e-mail, and packetization updates. This, however, can result in data being lost. In the event that, e.g., vocoded audio packets are being transmitted, audio is sometimes discarded or an audio gap is introduced when a vocoded frame buffer is still being filled with frames, but has not yet been transmitted, at the time of the reselection. Alternatively, audio sometimes discarded or an audio gap is introduced when a vocoded frame packet has not yet completed transmission at the time of the reselection. Another problem is that sometimes certain types of frames of video data are transmitted that indicate only the differences in the frame from the previous frame. Each time the differences from the previous frame are transmitted, there is a certain possibility of error that increases with each frame. During a reselection none of this incremental data can be transmitted. Therefore, in the event that an error is included/has occurred in any of the previous frames up until the last “full frame” (i.e., the most recent frame which does not indicate incremental differences between a previous frame), the erroneous video frame data may be utilized for the duration of the reselection, which may result in erroneous video data being viewed at a target mobile station for an extended period of time.
Another problem that can arise occurs when the mobile station is in a sector or is communicating with a base station that is currently experiencing high throughput, but is about to experience a reselection that would result in the mobile station communicating with another base station or sector having a much lower throughput. Consequently, in the event that the mobile station needs to synchronize data such as an email application, this synchronization may not be possible or will be less efficient in the second sector or base station.
Another problem that can arise occurs when the mobile station is in a sector or is communicating with the station that is currently supporting a larger number of other mobiles which are interested in the same broadcast content over a short channel, but is about to experience a reselection would result in the mobile communicating with another base station or sector which has no other mobiles interested in the same broadcast content. An example of this broadcast content might be a video news update. Consequently, in the event that the mobile station needs to download this video news update, the synchronization is less efficient under the second sector or base station, because there are no other mobiles which can share a share channel with that mobile in the second base station.
Current systems do not anticipate these potential problems or take corrective actions to avoid service disruption.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.